Summary Acute respiratory distress syndrome (ARDS) imposes high mortality and long-term effects on patient quality-of- life. Circulatory shock secondary to sepsis is the leading cause of ARDS. Extracorporeal membrane oxygenation (ECMO) and protective ventilation strategies are the current standards of care; yet provide support only for innate mechanisms of healing. While these supportive therapies are helpful, they offer little improvement in overall mortality for severe ARDS. Currently, no methods exist for targeted treatment for the rapid rehabilitation of lungs affected by ARDS. To address this, our laboratory has designed a novel in vivo lung perfusion (IVLP) technique for the perfusion of lungs in vivo with Steen solution in a preclinical porcine model of ARDS, which allows for targeted lung rehabilitation. This technique involves cannulation of the pulmonary artery (inflow) and pulmonary veins (outflow) of the injured lung to enable closed-circuit perfusion and direct treatment. This technique combines the benefits of ECMO and ex vivo lung perfusion (EVLP, used to assess marginal donor lungs for transplant) to provide a platform upon which injured lungs can be treated in vivo with targeted therapies in an isolated fashion without the potential risks of systemic treatment. Clinically, IVLP would be performed in a percutaneous fashion that could function as an adjuvant to ECMO therapy to shorten duration of support resulting in reduced morbidity and mortality. IVLP represents a novel method of therapy to reduce the severity of ARDS secondary to trauma or septic shock. Our prior experience with both EVLP and ILVP strongly suggest that injured lungs can be successfully rehabilitated utilizing IVLP targeted therapy. This proposal will test the hypothesis that IVLP with Steen solution will rehabilitate lungs with LPS-induced ARDS in a preclinical porcine model with subsequent development of percutaneous techniques for this therapy. Specific Aim 1 will optimize the rehabilitative capacity of IVLP using a porcine model of LPS-induced lung injury. This will be accomplished through experiments that will optimize timing, confirm durability, and improve perfusion strategies. Specific Aim 2 will use in vitro models using pulmonary microvascular endothelial cells and alveolar epithelial cells to define mechanisms for the protective effects of Steen solution on the alveolar-capillary barrier during IVLP. Specific Aim 3 will demonstrate the feasibility of percutaneous IVLP for the treatment of severe ARDS, which will be necessary for clinical translation. Our recent studies with IVLP demonstrate the feasibility and efficacy of IVLP for the treatment of ARDS, representing a major paradigm shift in the management of ARDS. If successful, our proposed studies will define EVLP as a novel, viable platform for targeted therapy of ARDS and will lead a path for translation into human studies.